Within the field of wind turbines it is necessary to perform work on parts that is situated at a considerable height above ground level (or sea level, when sea wind turbines are concerned) such as e.g. repair of rotor blades, the surface of these, surface treatment of rotor blades and the tower etc. Further, it has been recognized that it is advantageous or even necessary to clean such parts and in particular the rotor blades in order to maintain good results as regards the power efficiency. Further, it may be advantageous to perform other forms of maintenance in order to achieve good power production results and optimal economic results, such as e.g. surface treatments, inspection etc.
In order to perform such work a number of hoisting arrangements have been proposed in the prior art.
Such a hoisting arrangement is known from German utility model DE 296 03 278 U in which suspension means are fastened to each of the two rotor blades near the hub of the rotor once the windmill has been brought to a stop and with one rotor blade pointing straight downwards. A special work platform with a through-going slit at the bottom has been fixed to these suspension means so that the rotor blade pointing downwards could be inserted into this slit. The work platform has subsequently been hoisted upwards in a stepwise manner, while the crew has rinsed the surface of the rotor blade manually, e.g. with one person located on each side of the rotor blade.
Even with such an arrangement, it is a time-consuming process to carry out a cleaning of the rotor blades of a windmill, just as such a known arrangement would probably require the use of machinery, such as a crane, for fixation of the suspension means. Further, the platform itself will have a considerable weight and size, thereby leading to further costs and use of heavy machinery for lifting and lowering the platform.
Devices of corresponding kind are known from DE 199 09 698 A1 and DE 43 39 638 A1, which are encumbered with the same disadvantages as those mentioned above, including that extensive use must be made of special material such as cranes, for example mobile cranes, or relatively comprehensive materials which, for example, are mounted on the turbine tower beforehand.
Further, these prior art systems are generally not configured in a manner facilitating user-friendliness and do not provide the personnel with an optimal safety environment.
Thus, it is an objective of the invention to provide an improved device for performing such work at a structure such as a wind turbine, e.g. on a rotor blade or on a wind turbine tower.
It is a further objective to provide such a device whereby improved user-friendliness and safety may be achieved.
A further objective is to provide such a device that allows access to virtually all parts of e.g. a rotor blade with relatively simple and few means.
It is also an objective to provide such a device that may be designed as a relatively light structure and in relatively light materials while maintaining safety standards and even provide improvements in safety aspects.
These and other objectives are achieved by the invention as explained in detail in the following.